We pay a fortune to get people to our web, publish content and invest time and money, but when they are finally there, a majority comes and goes. There are techniques to identify and retain people on the web, but what works traditionally well are web pop-ups. Everybody says they never filled a pop-up (including me!), but they do. According to our experience, pop-ups could grab contacts (e.g., emails) from 5-20% of visitors, in some case even more.
But not every pop-up will work if you just put it on the web. It should not pop up too early - people came to the page to see the content, and they have to have enough time to evaluate whether the content is worth the time. There are some rules about what is the best time to show the pop-up, like 50% of the average time spent on the page or 30 seconds. Test what works best for your site. Make individual pop-ups relevant for the content of individual pages and don’t annoy visitors repeatedly. A particular category is exit pop-ups triggered when a visitor leaves the page. Many tools add pop-ups into your pages, you can e.g., use Incomaker’s intelligent and GDPR compliant pop-ups even for free.